This invention relates to a flow meter for measuring the rate or quantity of flow of tap water as a fluid flowing through a casing.
Flow meters of this type have a casing which is provided with inlet and outlet ports and a measuring chamber containing therein a vane wheel. A fluid introduced into the measuring chamber through the inlet port rotates the vane wheel, and the number of rotations is measured by a measuring mechanism disposed over the measuring chamber. Then, an indicator section including a counter visually indicates the measured quantity of flow or consumption. In this case, nozzles with a fixed cross-sectional flow area are generally formed aslant in the wall of the measuring chamber so as to correspond to the inlet and outlet ports, in order to cause the fluid positively to act on the vane wheel, thereby minimizing the instrumental error or the discrepancy between the flow quantity and its corresponding measured number of rotations of the vane wheel.
In a prior art flow meter 1 shown in FIGS. 1 to 3, an inlet nozzle 6 and an outlet nozzle 7 open into a measuring chamber 5 so as to correspond to an inlet port 3 and an outlet port 4 of a casing 2 of the meter 1. The inlet and outlet nozzles 6 and 7 extend aslant along axes X--X and Y--Y (FIG. 3), respectively, and tangential to the rotating direction of a vane wheel 8. A fluid or tap water to be measured is led into a measuring chamber 5 through the inlet nozzle 6 to rotate the vane wheel 8. The rotation of the vane wheel 8 is transmitted through its supporting shaft 9 to a measuring mechanism 10 formed of a number of gears. The measurement result is visually indicated by an indicator section 12 (FIG. 1) including a counter 11.
In the conventional meter of this type, instrumental errors are adjusted by a pair of adjusting plates 13 and 14 having the vane wheel 8 in the measuring chamber 5. The adjusting plates 13 and 14 are intended to adjust the so-called forward flow. In adjustment, the adjusting plates 13 and 14 are moved symmetrically. Each of the adjusting plates 13 and 14 can rock around its shaft 16, and can also be fixed to a fixed supporting plate 15 in a suitable angular position by retaining means 17 formed of a setscrew and a slot. Thus, the action of the fluid on the vane wheel 8 may be controlled by changing the angular positions of the adjusting plates 13 and 14 to adjust the resistance against the incoming fluid.
The vane wheel 8 is rotatably supported by a pivot 18 fixed to the casing 2. The pivot 18 is fixed upright in the center of the measuring chamber 5 by means of a supporting member 20 screwed in a tapped hole 19 in the bottom of the measuring chamber 8 and a nut 21 fitted on the lower end portion of the pivot 18.
The casing of the meter of this type is generally formed by casting a metal such as bronze, and the nozzles are formed by machining afterwards. However, the nozzles must be accurately worked in a slanting manner, as shown in FIG. 3, requiring hard and complicated machine work.
With use of the adjusting plates of the prior art meter, instrumental error adjustment for the forward flow side may exert an influence on adjustment for the counter flow side, and it is difficult to make proper, well-balanced adjustment for both flow directions. This is an inevitable situation so long as the flow resistance is controlled for adjustment. Usually, therefore, a method is adopted in which the instrumental errors on the forward flow side are minimized at the sacrifice, in some measure, of the adjustment for the counter flow side.
The use of the adjusting plates widens the inside space of the measuring chamber, constituting a hindrance to the miniaturization of the meter as a whole.
Moreover, the manner of pivot fitting requires a tapped hole in the casing and troublesome assembly work for fitting the pivot in the tapped hole. Since the fitting portion of the pivot is complicated in structure, replacement of the pivot once set in place requires troublesome work, such as removal of the supporting member from the tapped hole. Thus, the construction and operation of the meter need be simplified or facilitated.